import java.util.Scanner;

public class Work02 {

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        //在此输入您的代码...
        long a,b,c;
        a = scan.nextLong();
        b = scan.nextLong();
        c = scan.nextLong();
        int day = 0;
        int week = 0;
        long weekWork = 5*a +2*b;
        long num = 0;
        while(num < c && c - num > weekWork){
            week++;
            num += weekWork;
        }
        // 还差不到一周或者刚好一周的工作量就可以刷完c道题
        if(c - num == weekWork){
            week++;
        }else if(c - num < weekWork){
            while(num < c){
                day++;
                if(day % 7 == 6||day%7 == 0){
                    num += b;
                }else{
                    num += a;
                }
            }

        }
        System.out.println(week*7+day);

        scan.close();
    }

}
